Construction 3D Printing

Construction 3D Printing 1
CONSTRUCTION 3D PRINTING
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Construction 3D Printing 2
Table of Contents
Introduction...............................................................................................................................................3
What is 3D Printing?.................................................................................................................................3
3D Printing Processes................................................................................................................................4
Stereolithography (SLA).......................................................................................................................4
Selective Laser Sintering (SLS)............................................................................................................5
Fused Deposition Modelling (FDM).....................................................................................................7
Inkjet Powder Printing.........................................................................................................................8
Construction 3D Printing Technologies...................................................................................................9
Contour Crafting...................................................................................................................................9
D-Shape................................................................................................................................................11
Concrete Printing................................................................................................................................12
Emerging objects.................................................................................................................................12
Concrete On-Site 3D Printing (CONPrint3D)...................................................................................13
Advantages of Construction 3D Printing...............................................................................................14
Disadvantages of Construction 3D Printing..........................................................................................14
Performance of 3D Printed Concrete.....................................................................................................15
Impact of 3D Printing on the Construction Industry...........................................................................16
Sustainability of 3D Printing in Construction Industry....................................................................16
Employment and labour impacts.......................................................................................................17
Logistics and Cost of 3D Printing vs. Traditional Construction......................................................17
Issues affecting the Implementation of 3D printing in the Construction Industry.............................18
Suitable Applications of 3D Printing in the Construction Industry....................................................18
Current Applications of 3D Printing..................................................................................................18
Future Applications of 3D Printing....................................................................................................19
References................................................................................................................................................21

Construction 3D Printing 3
Introduction
3D printing is one of the most advanced technologies revolutionizing the construction
industry. Previously, this technology was prevalent in the manufacturing sector but it is now
being applied in the construction industry (Wu, Wang & Wang, 2016). This paper investigates
different aspects of 3D technology as applied in the construction industry. The information will
give a true picture of the role that 3D printing is playing in the construction industry and its
future prospects.
What is 3D Printing?
3D printing refers to the technique of creating 3D objects from a prototype in a digital file
(Greenhalgh, 2015). In this process, the physical 3D objects are created or built one layer after
the other – a process referred to as additive (Kamran & Saxena, 2016); (Ya, et al., 2018). 3D
printing involves three main steps. First is the preparation process where a 3D model of the
object to be created is designed. Second is the actual 3D printing process that is done using a 3D
printer. In this process, the 3D printer is instructed by the 3D digital file on how to build the 3D
object (Kitsakis, et al., 2016). Third is the finishing process that involves sanding, lacquering or
panting the printed object so as to achieve the desired final object (Sculpteo, (n.d.)). 3D printing
is also referred to as additive manufacturing (AM) and it has numerous applications in sectors
such as education, automotive, manufacturing, construction, aerospace, biomedical (Melchels, et
al., 2010), food (Carla & Atonio, 2016), consumer products, and fashion, among others (Yeole,
et al., 2016).

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3D Printing Processes
Stereolithography (SLA)
SLA is one of the earliest and most common 3D printing processes. The present-day
layered technique of SLA was first invented by Hideo Kodama, a Japanese researcher, in early
1980s where he cured photosensitive polymers using ultraviolet (UV) light. A patent for SLA
process was filed by French investors Jean Claude Andre, Olivier de Witte and Alain Le
Mehaute in 1984 but it was not successful. However, SLA was patented later in 1984 by Charles
Chuck Hull as a process of creating 3D objects using UV light to build successive thin layers of
the object from bottom to top. Since then, the process has been improved and is now widely used
in manufacturing and other sectors.
SLA is a 3D printing process where photopolymer resin or liquid is exposed to UV light
to harden and create the desired objects. In this process, a vat filled with liquid polymer resin
gets exposed to a UV laser beam that is able to trace the 3D model image layer onto the resin, as
shown in Figure 1 below. This exposure hardens the resin layer through polymerization. After
that, the build platform rises again, exposing the resin to the laser beam. The process continues
until the desired object is built one layer after the other.

Construction 3D Printing 5
Figure 1: Illustration of SLA process (WhiteClouds, 2017)
Advantages of SLA process include: it can create both small and large objects with very
high precision and quality surface finish; it creates functional parts quickly (within a few hours
or days) depending on their size and complexity; can create objects with specific properties using
different materials; can create objects of any shape; minimizes material wastage; and it creates
strong parts. Disadvantages of SLA include: it only works with photopolymer materials, which
are not stable over time; the process is limited to producing only three parts at a time hence not
suitable for mass production; the parts created are more fragile because materials used are resins
(Schmidleithner & Kalaskar, 2018); and the cost of most SLA machines used is still high.
Selective Laser Sintering (SLS)
SLS is a 3D printing process that was invented and patented in 1986 by Dr. Carl Deckard
and Dr. Joe Beaman at the University of Texas. Since then, this process has been improved to
work with different materials including ceramics, plastics, glass, metals and composites.
The print process of SLS starts by a laser scanning the 3D model’s cross-section followed
by dispersing a thin layer of polymer powder on top of a build platform inside the chamber. The
powder gets preheated by the printer to a temperature that is just below the material’s melting
point. In the process, the particles gets fused mechanically forming a solid part. The powder that
remains unfused is used for supporting the solid part being created during printing thus
eliminating the necessity for dedicated support structures. After the first layer has been created, it
gets lowered by the platform into the build chamber then a new layer of powder is applied by a
recoater on top (Yap, et al., 2015). This process is repeated until all layers of the solid part are
created. Thereafter, the parts are left to cool inside the 3D printer after which they are removed

Construction 3D Printing 6
and transferred to a cleaning station for cleaning and other post-processing activities (Palermo,
2013). The summary of SLS system is shown in Figure 2 and 3 below.
Figure 2: Illustration of SLS process (Formlabs, (n.d.))
Figure 3: SLS Process (Shirazi, et al., 2015)
Some of the advantages of SLS include: its self-supporting system allows printing of
parts with highly complex geometries (Kumar, 2014); it creates very strong, stiff and durable
parts; resists strong chemicals; it allows a wide range of finishing processes (Gokuldoss, et al.,
2017); it is a very quick 3D printing technique; and it allows use of different materials (Tiwari, et
al., 2015). Despite these advantages, SLS also has some disadvantages, which include: it creates